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BDS3 Orthodontics > Normal dental development, Tooth eruption and Interceptive ortho > Flashcards

Normal dental development, Tooth eruption and Interceptive ortho Flashcards

1
Q

At birth what are the characteristics of the mouth?

A
  • Gum pads
  • Upper rounded
  • Lower is U shaped
  • Appear Class II
  • AOB
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2
Q

What is the eruption pattern of deciduous teeth?

A
  • Erupts from 6months to 2.5years
  • a-b-d-c-e
  • Lowers before uppers
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3
Q

What are the characteristics of deciduous dentition?

A
  • Incisors more upright
  • Spaced
  • Wear
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4
Q

What is a natal/ neo-natal tooth?

A
  • Abnormal dental development
  • Lower incisors (most common natal tooth) present at, or just after birth
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5
Q

When should a natal/neo-natal tooth be extracted?

A
  • If it is mobile and presents risk of inhalation
  • Is causing difficulty breastfeeding
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6
Q

What are the processes of tooth eruption?

A
  • Pre-eruptive phase
  • Eruptive phase
  • Post-eruptive phase
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7
Q

What is the pre-eruptive phase?

A
  • Starts when crown starts to form
  • Ends when crown formation complete/ root formation about to start
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8
Q

What is the eruptive phase?

A
  • Starts when root starts to form
  • Ends when teeth reach occlusal plane
  • Split into Intra-osseous stage and Extra-osseous stage
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9
Q

What is the post-eruptive phase?

A
  • Tooth movement/ eruption continues as root forms and throughout life in extremely small increments
  • Movement after tooth has reached occlusal plane
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10
Q

What are the characteristics of Pre-eruptive phase?

A
  • Developing crowns move constantly in jaw
  • Small mesial and distal movement occur
  • Developing crowns reposition themselves in response to increasing length, width and height of jaws
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11
Q

Where does the movement of tooth crowns occur in pre-eruptive phase?

A
  • Contained within bony crypts
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12
Q

What does movement of tooth occur in response to during eruptive phase?

A
  • Positional changes of neighbouring crowns
  • Growth of mandible and maxilla
  • Resorption of deciduous tooth roots
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13
Q

What occurs during Intra-osseous eruptive phase?

A

Root formation - starts with proliferation of epithelial root sheath and continues with production of dentine and pulp

Movement of developing tooth - in occlusal or incisal direction (slow)

Reduced enamel epithelium fuses with oral epithelium

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14
Q

What occurs during extra-osseous eruptive phase?

A

Penetration of tooth’s crown tip through epithelial layers (fast 1-2weeks)

Crown continues to move through mucosa in occlusal direction until contacts opposing tooth (slow several months)

Environmental factors like muscles forces from cheeks, lips and tongue help determine final tooth position

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15
Q

What is the eruption pathway?

A
  • Within dental follicle degeneration occurs
  • Blood vessels decrease
  • Nerve fibres break up into pieces
  • This area is eruption pathway
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16
Q

What is the Gubernacular cord?

A
  • Fibres from dental follicles formed in periphery of eruption pathway
  • Theory is it guides teeth to erupt in oral cavity
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17
Q

What happens to the bone during Intra-osseous eruptive phase?

A
  • Adjacent to and overlying, teeth bone loss keeps pace with occlusal movement of teeth
  • Osteoclasts and osteoblasts constantly remodelling bone
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18
Q

Why does post-eruptive movement occur?

A
  • In response to increases in height of growing alveolar bone
  • In response to attrition and abrasion (due to occlusal wear)
  • In response to loss of opposing teeth (can cause over-eruption)
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19
Q

What does proximal surface tooth wear lead to?

A
  • Mesial drift
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20
Q

What causes teeth to erupt?

A
  • Multifactorial and likely combo of;
  • Root formation
  • Remodelling of alveolar bone
  • Development of periodontal ligament (membrane)
  • Genetics
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21
Q

What are the roles of dental follicle?

A
  • Initiates resorption of bone overlying teeth
  • Facilitates connective tissue degradation and creates eruption pathway
  • Promote alveolar bone growth at base of tooth
  • Provides traction forces within PDL
  • Ectomesenchymal cells from dental follicle contribute to root formation
22
Q

What is Interceptive orthodontics?

A
  • Any procedure that will reduce or eliminate severity of developing malocclusion
23
Q

When can ectopic upper permanent canines be treated with interceptive ortho?

A
  • Extraction of deciduous canine ages 10-13
24
Q

Why would we intercept early mixed dentition?

A
  • Impacted 6’s
  • Potential crowding
  • Early loss of deciduous teeth
  • Carious 6’s
  • Cross-bites
  • Transposed teeth
  • Habits
25
Q

When is the best time to extract deciduous to encourage permanent teeth to erupt?

A
  • 1/2 to 2/3rds root development of permanent tooth
26
Q

What are the eruption dates?

A

6’s = 6years
1’s = 7years
2’s = 8years
4’s = 10years
3’s and 5’s = 11-12years
7’s = 12-13years

27
Q

How is space created for larger anterior teeth from decidious?

A
  • Increased in intercanine width though lateral growth of jaws
  • Upper incisors erupting onto wider arc (more proclined)
  • Leeway space
28
Q

In relation to primary teeth how do the permanent incisors erupt?

A
  • Develop palatal/lingual to primary teeth
29
Q

How is leeway space calculated for upper arch?

A

(c+6+7) - (3+4+5) = 1to1.5mm

30
Q

How is leeway space calculated for lower arch?

A

(c+6+7) - (3+4+5) = 2to2.5mm

31
Q

What is a diastema?

A
  • Space separating two upper centrals
32
Q

What is the prevalence of diastema?

A

6Yrs 96% have diastema
12years 7% have diastema as 3’s erupted
- If <2.5mm should close

33
Q

How can ectopic eruption affect first permanent molar?

A
  • Permanent first molar gets stuck behind e
  • Fails to fully erupt
34
Q

What are the management options for ectopic eruption of e?

A
  • If <7 years wait 6months (90% self correct)
  • Orthodontic separator
  • Attempt to distalise first molar
  • Extract E
  • Distal disking of e
35
Q

What to do if unerupted central incisors?

A
  • Case history e.g. regarding trauma
  • E/O and I/O
  • Palpate labially and palatally
  • If primary retained, is it mobile/discoloured
  • Radiograph PA / AOM
36
Q

What are the management options for supernumerary unerupted central incisor?

A
  • Remove primary teeth and supernumerary
  • Create/ maintain space
  • Monitor 12months (<9= immature root apex)
  • Expose/bond gold chain and apply orthodontic traction if still unerupted
37
Q

What is balancing extraction?

A
  • Removal of tooth from opposite side of same arch
  • To maintain position of dental centreline (preserve symmetry)
38
Q

What is compensating extraction?

A
  • Removal of tooth from opposing quadrant
  • To maintain buccal occlusion
39
Q

What does early loss of deciduous teeth cause?

A
  • Localised crowding
40
Q

What is the management of early loss of A’s and B’s?

A
  • Has little impact
  • Don’t balance or compensate
41
Q

What is the management of early loss of C’s?

A
  • Balance
  • Compensating extraction not required
42
Q

What is the management of early loss of D’s?

A
  • Small CL
  • Shift, balance under GA?
43
Q

What is the management of early loss of E’s?

A
  • tend not to balance
  • Major space loss
  • Upper > lower
  • Consider space maintainer
44
Q

What are the two types of space maintainers?

A
  • Removable (passive URA)
  • Fixed (palatal and lingual arches/ band and loop)
45
Q

What do you need to consider when extracting first molars of poor prognosis?

A
  • Age/stage of dental development
  • Degree of crowding
  • Malocclusion type
  • Condition of other teeth
  • LA or GA
46
Q

What conditions give most ideal result when extracting first molars?

A
  • 7’s bifurcation calcifying
  • 8’s present
  • Class I av/reduced OB
  • Moderate lower crowding
  • Mild/mod upper crowding
47
Q

What are the general rules to follow when extracting 6’s in Class I patient?

A
  • If extract lower take upper
  • Don’t balance with sound tooth
  • Don’t balance if well aligned or spaced
  • If extract upper don’t need to take lower
48
Q

When should you treat a posterior unilateral cross bite?

A
  • IOTN 4c
  • > 2mm
49
Q

What is a URA to help fix posterior unilateral cross bite?

A
  • Active component is Hyrax screw or coffin spring
  • Retention is no retentive component across midline
  • Baseplate is Posterior bite plane to disclude teeth
50
Q

What is the digit habit management?

A
  • Positive reinforcement
  • Bitter-tasting nail varnish
  • Glove on hand, elastoplast
  • Habit breaker appliance (habit deterrent) fixed or removable

BDS3 Orthodontics (10 decks)

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